1. Field of the Invention
The present invention relates to (i) a driving device for a display panel in which a pixel composed of sub-pixels of red (R), green (G), blue (B), and at least one other color has a plurality of sub-pixels at least in a vertical scanning direction, and color filters are provided corresponding to the respective sub-pixels, and (ii) a display device including the driving device.
2. Description of the Related Art
As disclosed in Japanese Unexamined Patent Publication No. 118521/1990 (Tokukaihei 2-118521; published on May 2, 1990), for example, the conventional liquid crystal display devices have blocks of color filters arranged in a pattern of locations for the increase of luminance. Each of the blocks is composed, as a unit block, of a color filter of white (W) as well as color filters of red (R), green (G), and blue (B). More specifically, in the liquid crystal display devices, white light is emitted from a backlight such as a fluorescent lamp, for example, passes through liquid crystal to change its transmittance. Then, the white light passes through the color filters of red (R), green (G), and blue (B), whereby a color image is recognized by human eyes. The light having passed through the color filters of red (R), green (G), and blue (B) reduces a considerable amount of luminance. For that reason, by adding the color filter of white (W) to one block, it is possible to increase luminance of light emitted by one block.
As illustrated in FIG. 17, Patent Document 1 mentioned above adopts a 2-by-2 sub-pixel matrix pattern as a pattern of colors red (R), green (G), blue (B), and white (W). The 2-by-2 sub-pixel matrix pattern is arranged such that blocks, each of which is composed of red (R), blue (B), white (W), and green (G) in this order counterclockwise, are arranged in a matrix manner.
Assume that one block, i.e. one pixel composed of sub-pixels of red (R), green (G), blue (B) outputs luminance of 1 in the conventional arrangement. On the contrary, a block composed of sub-pixels of red (R), green (G), blue (B), and white (W) arranged in a matrix manner obtains a total luminance of (¾)×1+(¼)×3=3/2. This is because luminance of ¾ is obtained from the three sub-pixels of red (R), green (G), and blue (B), which occupy ¾ area of one pixel, and luminance of 3 is obtained from the sub-pixel of white (W), which occupies ¼ area of one pixel. This makes it possible to realize luminance increase of approximately 50% per pixel as a whole.
Another example of the pattern includes a stripe layout pattern illustrated in FIG. 18 and a 2-by-2 pixel matrix pattern as illustrated in FIG. 19. In the 2-by-2 pixel matrix pattern, four pixels constituting one block are arranged in a matrix manner.
In a color filter 100 arranged in the 2-by-2 pixel matrix pattern, pixel (1,1) and pixel (2,1) each has red (R), blue (B), green (G), and white (W) in this order counterclockwise, whereas pixel (1,2) and pixel (2,2) each has blue (B), red (R), white (W), and green (G) in this order counterclockwise. Such a pixel arrangement is made for the following reason:
That is, white (W) generally contributes to luminance only. Among red (R), green (G), and blue (B), green (G) contributes to luminance most, followed by red (R) and blue (B). Red (R), green (G), and blue (B) contribute to hue equally. Meanwhile, there is the fact that a human is sensitive to luminance and able to recognize even a slight variation of luminance, but is not able to recognize slight variation of hue.
Thus, if four pixels are arranged per block in consideration of luminance balance that is important for a human, the above-mentioned 2-by-2 pixel matrix pattern is obtained, for example.
However, (i) a driving device for a liquid crystal display panel including color filters arranged in the conventional matrix pattern of 2-by-2 sub-pixels and (ii) a liquid crystal display device including the driving device have the following problem. That is, it is difficult to respond to, for example, scale change of a screen or other event because incoming signals are in one-to-one correspondence with display outputs. As a result, it is difficult to respond to scale change, especially scale change in a longitudinal direction, as in the present situation.
For example, the number of effective scanning lines of a typical television is currently 480, whereas the number of effective scanning lines of a digital high-definition television is 1080. Under the circumstances, a typical television cannot display an image corresponding to video signals having 480 or more effective scanning lines, with a resolution determined by the video signals.
Further, video image corresponding to even 480 lines of TV data can be displayed on a display device with a higher degree of definition than its original video image if the display device has a capability of displaying, for example, 960 lines of data, which is twice as much as 480 lines of TV data. This is not limited in a case where scale change is not performed. Deterioration of image that can occur due to video format change to 720 lines, 1080 lines, or other number of lines can be minimized if there is a device capable of high-definition display.
Interpolation of one pixel for improvement in resolution is disclosed in Japanese Unexamined Patent Publication No. 64579/2004 (Tokukai 2004-64579; published on Feb. 26, 2004) and Japanese Unexamined Patent Publication No. 208339/2004 (Tokukai 2004-208339; published on Jul. 22, 2004), for example. Both cases assume a stripe pattern and fail to disclose a displaying method that places importance on luminance improvement, luminance balance, and color center. In other words, there is no structure for a resolution which allows for display of interpolated information and is higher than a resolution determined by incoming signals, in the stripe pattern. That is why it is impossible to provide means displaying an interpolated high-definition image. On the contrary, color filters arranged in a matrix pattern of 2-by-2 sub-pixels per pixel has the potential to perform display with a high resolution, which is, however, complex and is not easy.